Skip to main content

Full text of "Treatise On Applied Analytical Chemistry(Vol-1)"

See other formats



1.  Insoluble Substances.—A few grams are dissolved in water and
the solution filtered through a tared filter, which is then treated in the
ordinary way.

2.  Water.—2-3 grams are heated at 100-105° to constant weight.

3.  Sulphates.—Tested for as in potassium dichromate (q.v.} and deter-
mined as barium sulphate.

4.  Determination of the Chromic Anhydride.—As with potassium
dichromate (q.v.}.

Pure crystallised sodium dichromate contains 67% of CrO3, and the anhydrous
salt 76-4%.    The fused commercial product usually contains 73-74% CrO3.


NaOH = 40

This is sold in lumps, sticks or powder, and in various degrees of purity
(Caustic soda from sodium, by alcohol, by lime, -pitrified, crude). The com-
monest impurities, often in considerable quantities, are carbonates, sul-
phates, chlorides, nitrates, alumina, ferric oxide and lime; these are
detected as in caustic potash.

The strength is determined by measuring the total alkalinity and the
alkalinity after treatment with barium chloride (methyl orange used) as
indicated under " Sodium carbonate " : i c.c. N-acid = 0-04 gram NaOH
or 0-031 gram Na20 or 0-053 gram Na2C03.

* *

Sodium hydroxide pure from metal represents the best quality sold, and should
contain only traces of chlorides and at most 5% of water.

Sodium hydroxide by alcohol should answer the same requirements as potas-
sium hydroxide by alcohol, and should not contain more than 5% of water.

In sodium hydroxide by lime the total alkalinity should not be less than 90%
and the content of carbonate not greater than 5%.

The strength of caustic soda for soap works is usually expressed as Na2O
(i c.c. N-acid = 0-031 gram Na2O). In that of 60-65 strength, 3% of carbonate
is allowable and in that of 70-77 strength, 1-5% of carbonate.

See Fertilisers


This is sold in white or yellowish crystals or cast rods and is extremely
soluble in water and moderately so in alcohol. It usually contains very few
impurities and its value depends essentially on the content of NaN02.

Quantitative Determination (Lunge's method).— A seminormal
permanganate solution is prepared by dissolving 15-82 grams of chemically
pure potassium permanganate in water to i litre, the titre being controlledgnesium chlorides and sulphates) are allowed by the Union ol;